Charging system, battery pack, and charger

ABSTRACT

In one aspect, the present disclosure discloses a charging system including a battery pack and a charger. The battery pack includes a first battery pack terminal, a second battery pack terminal, and a third battery pack terminal. The second battery pack terminal is spaced apart from the first battery pack terminal in an intersecting direction. The intersecting direction intersects a removal direction of the battery pack from the charger. The charger includes a first charger terminal, a second charger terminal, and a third charger terminal. The second battery pack terminal is arranged so as to pass through an area spaced apart from the third charger terminal in a process of removing the battery pack from the charger.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Japanese Patent Application No.2018-225649 filed on Nov. 30, 2018 with the Japan Patent Office, thedisclosure of which is incorporated herein by reference.

BACKGROUND

The present disclosure relates to a battery pack.

Japanese Patent No. 5523905 discloses a battery pack attachable to andremovable from a charger and an electric power tool. This battery packis provided with two terminals aligned in a direction where the batterypack is removed from the charger or from the electric power tool.

SUMMARY

In recent years, the capacity of a battery in a battery pack used for anelectric power tool has become increasingly larger. As the capacity ofthe battery is increased, the battery pack's electrical configuration tocharge the battery becomes complicated. As a result, the number ofterminals to be connected to a charger or to an electric power tool maybe increased in the battery pack. Such increase in the number of theterminals may lead to a larger-sized battery pack.

One conceivable way of inhibiting the larger-sized battery pack causedby increase in the number of the terminals is to arrange two or moreterminals in alignment in a removal direction of the battery pack asdisclosed in the above-described Japanese Patent No. 5523905.

However, arranging the two or more terminals in alignment in the removaldirection may cause the following problem. Specifically, in the processof removing the battery pack from the charger, a certain terminal in thecharger removed from a counterpart terminal in the battery pack maycontact a non-counterpart terminal in the battery pack. Such contact ofthe non-counterpart terminal with the terminal of the charger in theremoval process may lead to a malfunction of the charger depending on anelectrical state of the non-counterpart terminal.

It is desirable that the present disclosure enable, in one aspectthereof, inhibition of occurrence of a malfunction of a charger causedby contact of a terminal of the charger with a terminal of a batterypack being removed from the charger.

In one aspect, the present disclosure discloses a charging system. Thischarging system includes a battery pack and a charger. The battery packis configured to be removably attached to an electric working machine.The charger is configured such that the battery pack is removablyattached thereto.

The battery pack includes a battery, a first battery pack terminal, asecond battery pack terminal, a third battery pack terminal, and/or astate setting circuit. The battery is configured to be charged withcharging power supplied from the charger. The first battery packterminal has a first electrical characteristic. The second battery packterminal has a second electrical characteristic, or is configured tohave the second electrical characteristic depending on an operatingstate of the battery pack. The second battery pack terminal is spacedapart from the first battery pack terminal in an intersecting direction.The intersecting direction intersects a removal direction of the batterypack from the charger. Specifically, assuming that a vector extends fromthe first battery pack terminal as a starting point to the secondbattery pack terminal as an ending point, a direction indicated by thevector corresponds to a direction normal to the removal direction.Alternatively, the vector is expressed by a sum of a first vectorindicating the removal direction and a second vector indicating thedirection normal to the removal direction. The removal directioncorresponds to a direction in which the battery pack attached to thecharger is moved during removal of the battery pack from the charger.The third battery pack terminal is aligned (i.e., arranged in a line)with the first battery pack terminal or with the second battery packterminal in the removal direction. The state setting circuit sets, inresponse to the battery pack being in a presupposed operating state, anelectrical characteristic of the third battery pack terminal such thatthe third battery pack terminal has the second electricalcharacteristic.

The charger includes a first charger terminal, a second chargerterminal, a third charger terminal, and/or a functional circuit. Thefirst charger terminal is configured to be connected to the firstbattery pack terminal in response to attachment of the battery pack tothe charger. The second charger terminal is configured to be connectedto the second battery pack terminal in response to attachment of thebattery pack to the charger. The third charger terminal is configured tobe connected to the third battery pack terminal in response toattachment of the battery pack to the charger. The functional circuit isconfigured to perform a first function in response to connection of thethird battery pack terminal having the second electrical characteristicto the third charger terminal.

The second battery pack terminal is arranged so as to pass through anarea spaced apart from the third charger terminal in a process ofremoving the battery pack from the charger (hereinafter referred to as aremoval process).

In the thus-configured charging system, the third battery pack terminalis aligned (i.e., arranged in a line) with the first battery packterminal or with the second battery pack terminal in the removaldirection. The second battery pack terminal is arranged so as to passthrough the area spaced apart from the third charger terminal in theremoval process. In other words, the second battery pack terminal isarranged so as not to contact the third charger terminal in the removalprocess. This inhibits contact of the second battery pack terminalhaving the second electrical characteristic with the third chargerterminal in the removal process. Consequently, it is possible to inhibita malfunction of the charger (e.g., unintended performance of the firstfunction by the functional circuit) caused by such contact.

The state setting circuit may be configured to determine whether amalfunction is present. The malfunction may correspond to an event inwhich charging of the battery has to be stopped in the battery pack. Thepresupposed operating state may correspond to a state in which themalfunction is not present.

In the thus-configured charging system, it is possible to notify thecharger of whether the malfunction is present in the battery pack viathe third battery pack terminal and the third charger terminal duringcharging of the battery by the charger. The third charger terminal isarranged such that the second battery pack terminal does not contact thethird charger terminal in the removal process. Thus, in the removalprocess, the second battery pack terminal having the second electricalcharacteristic is inhibited from contacting the third charger terminal,to thereby further inhibit erroneous notification to the charger to theeffect that the battery pack is in the presupposed operating state.

The first function may include output of an operation permission signal.The charger may further include a charging circuit, an electric powerpath, a switch circuit, a switch control circuit, an enabling circuit,and/or a forcible interruption circuit. The charging circuit isconfigured to generate the charging power. The electric power path isconfigured to supply the charging power to the battery pack. The switchcircuit is configured to establish or interrupt the electric power path.The switch control circuit is configured to control the switch circuit.The enabling circuit is configured to enable control of the switchcircuit by the switch control circuit in response to output of theoperation permission signal. The forcible interruption circuit isconfigured to disable the control of the switch circuit by the switchcontrol circuit to thereby cause the switch circuit to interrupt theelectric power path, in response to no output of the operationpermission signal.

In the thus-configured charging system, if the battery pack is in thepresupposed operating state, control of the switch circuit by the switchcontrol circuit can be enabled in the charger. As described above, thethird charger terminal is arranged such that the second battery packterminal does not contact the third charger terminal in the removalprocess. Thus, in the removal process, a situation is inhibited in whichthe second battery pack terminal having the second electricalcharacteristic contacts the third charger terminal to thereby causeerroneous output of the operation permission signal from the functionalcircuit.

The state setting circuit may be configured to set the third batterypack terminal such that the third battery pack terminal has, as thesecond electrical characteristic, a first input impedance within aspecified range. The first battery pack terminal may have, as the firstelectrical characteristic, a second input impedance out of the specifiedrange. The second battery pack terminal may have a third input impedancewithin the specified range, or may be configured to have the third inputimpedance depending on the operating state of the battery pack.

In the thus-configured charging system, it is possible to easily notifythe charger that the battery pack is in the presupposed operating stateby controlling the input impedance of the third battery pack terminal.

The third battery pack terminal may be aligned with the first batterypack terminal in the removal direction (i.e., the terminals may bearranged in a line).

In the thus-configured charging system, the third battery pack terminalis not arranged in alignment with the second battery pack terminal inthe removal direction. Thus, the second battery pack terminal isappropriately inhibited from contacting the third charger terminal inthe removal process.

The third battery pack terminal may be aligned with the second batterypack terminal in the removal direction (i.e., the terminals may bearranged in a line). Further, the third battery pack terminal may bearranged on an opposite side of the removal direction with respect tothe second battery pack terminal.

In the thus-configured charging system, although the third battery packterminal is arranged in alignment with the second battery pack terminalin the removal direction, the third battery pack terminal is arrangedupstream of the second battery pack terminal in the removal direction(in other words, the second battery pack terminal is arranged downstreamof the third battery pack terminal in the removal direction). Thus, inthe removal process, the second battery pack terminal moves away fromthe third battery pack terminal in response to movement of the batterypack in the removal direction. This results in appropriate inhibition ofcontact of the second battery pack terminal with the third chargerterminal in the removal process.

In another aspect, the present disclosure discloses a battery pack. Thisbattery pack is configured to be removably attached to an electricworking machine and to a charger. The charger includes a first chargerterminal, a second charger terminal, and/or a third charger terminal.The battery pack includes a battery, a first battery pack terminal, asecond battery pack terminal, a third battery pack terminal, and/or astate setting circuit.

The battery is configured to be charged with charging power suppliedfrom the charger. The first battery pack terminal is configured to beconnected to the first charger terminal in response to attachment of thebattery pack to the charger. The first battery pack terminal has a firstelectrical characteristic. The second battery pack terminal isconfigured to be connected to the second charger terminal in response toattachment of the battery pack to the charger. The second battery packterminal has a second electrical characteristic, or is configured tohave the second electrical characteristic depending on an operatingstate of the battery pack. The second battery pack terminal is spacedapart from the first battery pack terminal in an intersecting direction.The intersecting direction intersects a removal direction of the batterypack from the charger. The third battery pack terminal is configured tobe connected to the third charger terminal in response to attachment ofthe battery pack to the charger. The third battery pack terminal isaligned (i.e., arranged in a line) with the first battery pack terminalor with the second battery pack terminal in the removal direction. Thestate setting circuit is configured to set, in response to the batterypack being in a presupposed operating state, an electricalcharacteristic of the third battery pack terminal such that the thirdbattery pack terminal has the second electrical characteristic.

The charger is configured to perform a first function in response toconnection of the third battery pack terminal having the secondelectrical characteristic to the third charger terminal. The secondbattery pack terminal is arranged so as to pass through an area spacedapart from the third charger terminal in a process of removing thebattery pack from the charger.

The thus-configured battery pack enables inhibition of contact of thesecond battery pack terminal with the third charger terminal in theprocess of removing the battery pack from the charger, to therebyfurther inhibit a malfunction of the charger caused by such contact.

In yet another aspect, the present disclosure discloses a charger. Thischarger is configured such that a battery pack is removably attachedthereto. The battery pack includes a first battery pack terminal, asecond battery pack terminal, and/or a third battery pack terminal. Thecharger is configured to supply charging power to the battery pack.

The charger includes a first charger terminal, a second chargerterminal, a third charger terminal, and/or a functional circuit. Thefirst charger terminal is configured to be connected to the firstbattery pack terminal in response to attachment of the battery pack tothe charger. The first battery pack terminal has a first electricalcharacteristic. The second charger terminal is configured to beconnected to the second battery pack terminal in response to attachmentof the battery pack to the charger. The second battery pack terminal hasa second electrical characteristic, or is configured to have the secondelectrical characteristic depending on an operating state of the batterypack. The second charger terminal is spaced apart from the first chargerterminal in an intersecting direction. The intersecting directionintersects a removal direction of the battery pack from the charger. Thethird charger terminal is configured to be connected to the thirdbattery pack terminal in response to attachment of the battery pack tothe charger. The third charger terminal is aligned (i.e., arranged in aline) with the first charger terminal or with the second chargerterminal in the removal direction. The third battery pack terminal hasthe second electrical characteristic in response to the battery packbeing in a presupposed operating state. The functional circuit isconfigured to perform a first function in response to connection of thethird battery pack terminal having the second electrical characteristicto the third charger terminal.

The third charger terminal is arranged so as to pass through an areaspaced apart from the second battery pack terminal in a process ofremoving the battery pack from the charger.

The thus-configured charger enables inhibition of contact of the secondbattery pack terminal with the third charger terminal in the process ofremoving the battery pack from the charger, to thereby further inhibit amalfunction of the charger (e.g., unintended performance of the firstfunction by the functional circuit) caused by such contact.

BRIEF DESCRIPTION OF THE DRAWINGS

An example embodiment of the present disclosure will be described belowwith reference to the accompanying drawings, in which:

FIG. 1 is an explanatory diagram showing an electrical configuration ofa battery pack of the embodiment;

FIG. 2 is an explanatory diagram showing an electrical configuration ofa charger of the embodiment;

FIG. 3 is an explanatory diagram showing an electrical configuration ofa working machine body of the embodiment;

FIG. 4 is an electric circuit diagram showing an ES terminal of thecharger and an ES terminal of the battery pack, and details of electriccircuits connected to these terminals;

FIG. 5 is an electric circuit diagram showing a Vcc terminal of thecharger and a Vcc/TFB terminal of the battery pack, and details ofelectric circuits connected to these terminals;

FIG. 6 is an electric circuit diagram showing a Tx terminal of thecharger and an Rx terminal of the battery pack, and details of electriccircuits connected to these terminals;

FIG. 7 is an explanatory diagram showing one example of terminalsarrangement in the charger and the battery pack, and showing a state inwhich the battery pack is completely removed from the charger;

FIG. 8 is an explanatory diagram showing a state in which the batterypack is moved in an attachment direction from a position shown in FIG. 7to initiate attachment of the battery pack;

FIG. 9 is an explanatory diagram showing a state in which the batterypack is further moved in the attachment direction from a position shownin FIG. 8;

FIG. 10 is an explanatory diagram showing a state in which the batterypack is further moved in the attachment direction from a position shownin FIG. 9 to complete the attachment of the battery pack to the charger;and

FIG. 11 is an explanatory diagram showing another example of terminalsarrangement in a charger and a battery pack.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS Example Embodiment

(1) Overview of Charging System and Electric Working Machine

A charging system and an electric working machine of the presentembodiment will be described with reference to FIGS. 1 to 3.

The charging system of the present embodiment includes a battery pack 10shown in FIG. 1 and a charger 40 shown in FIG. 2. The charger 40 isconfigured such that the battery pack 10 is attachable thereto andremovable therefrom.

As shown in FIG. 1, the battery pack 10 includes a battery 20. Thebattery 20 is a rechargeable battery. The battery 20 may be any kind ofrechargeable battery. In the present embodiment, the battery 20 is, forexample, a lithium-ion battery.

More specifically, the battery 20 includes a first cell group 21 and asecond cell group 22, which are connected to each other in series. Eachof the first cell group 21 and the second cell group 22 includes two ormore cells. The two or more cells may be connected to each other in anymanner. In the present embodiment, for example, the two or more cellsare connected to each other in series in each of the first cell group 21and the second cell group 22.

Rated voltage values of the first cell group 21 and the second cellgroup 22 may be any values. In the present embodiment, the rated voltagevalues of the first cell group 21 and the second cell group 22 are each,for example, 28.8 V, and a rated voltage value of the battery 20 is, forexample, 57.6 V. The first cell group 21 and the second cell group 22 ofthe present embodiment each include, for example, eight cells connectedto each other in series. A rated voltage value of each cell is, forexample, 3.6 V. An actual voltage value of the battery 20 may varyaccording to a charging state of the battery 20. Specifically, thevoltage value of the battery 20 may be a value lower than 57.6 V, andalso may be a value higher than 57.6 V (e.g., 64 V). The number of thecells in the battery 20 may be any number. The rated voltage value ofeach cell may be any value. The rated voltage value of the battery 20may be any value.

In response to attachment of the battery pack 10 to the charger 40, thecharger 40 performs data communication with the battery pack 10 toacquire various information on charging of the battery 20. The charger40 supplies charging power to the battery 20 based on the variousinformation acquired from the battery pack 10, to thereby charge thebattery 20.

The battery pack 10 is attachable to and removable from various electricapparatuses, such as a working machine body 200 (see FIG. 3) to bedescribed below. The battery pack 10 is configured to supply electricpower of the battery 20 (hereinafter referred to as “battery power”) tothe electric apparatus to which the battery pack 10 is attached.

The electric working machine of the present embodiment includes thebattery pack 10 shown in FIG. 1 and the working machine body 200 shownin FIG. 3. The working machine body 200 is configured such that thebattery pack 10 is attachable thereto and removable therefrom.

In response to attachment of the battery pack 10 to the working machinebody 200, the battery power is supplied to the working machine body 200.The working machine body 200 is operated with the battery power.

The working machine body 200 is configured to perform operations for anyof various applications, such as gardening, stone processing, metalprocessing, and wood processing. The electric working machine of thepresent embodiment may be, for example, a rechargeable brush cutter forcutting grass, small-diameter trees, and so on.

(2) Configuration of Battery Pack

As shown in FIG. 1, the battery pack 10 includes a positive terminal 11,a negative terminal 12, a center terminal 13, an error stop (ES)terminal 14, a transmission (Tx) terminal 15, a battery detection(BD)/tool shutdown (TS) terminal 16, a reception (Rx) terminal 17, aVcc/TFB terminal 18, and a trigger detection (TD) terminal 19.

The positive terminal 11 is connected to a positive electrode of thebattery 20 (specifically, a positive electrode of the first cell group21). The negative terminal 12 is connected to a negative electrode ofthe battery 20 (specifically, a negative electrode of the second cellgroup 22). The center terminal 13 is connected to a positive electrodeof the second cell group 22 of the battery 20 (in other words, anegative electrode of the first cell group 21).

The battery pack 10 further includes a battery control circuit 23, an ESoutput circuit 24, a Tx circuit 25, a BD/TS circuit 26, an Rx circuit27, an attachment detection circuit 28, a TD input circuit 29, apower-supply input circuit 30, a power-supply circuit 31, a voltagedetection circuit 32, a current detection circuit 33, and a temperaturedetection circuit 34.

The ES output circuit 24 is connected to the ES terminal 14. The Txcircuit 25 is connected to the Tx terminal 15. The BD/TS circuit 26 isconnected to the BD/TS terminal 16. The Rx circuit 27 is connected tothe Rx terminal 17. The attachment detection circuit 28 is connected tothe Vcc/TFB terminal 18. The TD input circuit 29 is connected to the TDterminal 19. The ES output circuit 24, the Tx circuit 25, the BD/TScircuit 26, the Rx circuit 27, the attachment detection circuit 28, andthe TD input circuit 29 are connected to the battery control circuit 23.

The voltage detection circuit 32 outputs battery voltage information tothe battery control circuit 23. The battery voltage informationindicates a value (hereinafter referred to as a “battery voltage value”)of voltage (hereinafter referred to as a “battery voltage”) of thebattery 20. The battery voltage information indicates, for example, avoltage value of the first cell group 21, a voltage value of the secondcell group 22, and/or a voltage value of the battery 20.

During discharge from the battery 20 to the electric apparatus, thecurrent detection circuit 33 outputs discharge current information tothe battery control circuit 23. The discharge current informationindicates a value of discharge current from the battery 20. Duringcharging of the battery 20 by the charger 40, the current detectioncircuit 33 outputs charging current information to the battery controlcircuit 23. The charging current information indicates a value ofcharging current supplied from the charger 40 to the battery 20.

The temperature detection circuit 34 detects a temperature of thebattery 20, and outputs temperature information to the battery controlcircuit 23. The temperature information indicates a temperature of thebattery 20 detected by the temperature detection circuit 34.

The battery control circuit 23 controls charging and discharge of thebattery 20 based on various information, such as the battery voltageinformation, the discharge current information, the charging currentinformation, and the temperature information. During charging of thebattery 20 by the charger 40, the battery control circuit 23 transmitsinformation required for charging to the charger 40, and/or receivessuch information from the charger 40 by performing data communicationwith the charger 40. The battery control circuit 23 calculates a valueof charging current required for charging the battery 20 based on, forexample, the battery voltage, and transmits a charging current commandvalue to the charger 40. The charging current command value indicatesthe value calculated by the battery control circuit 23.

The battery control circuit 23 includes a microcomputer including, forexample, a CPU and a memory. The memory may include a semiconductormemory, such as a RAM, a ROM, or a flash memory. The memory storesvarious programs and data to be read and executed in order for the CPUto achieve various functions of the battery pack 10. Such variousfunctions are not limited to the above-described software processing,and some or all of them may be achieved by hardware including acombination of logic circuits and analog circuits.

The power-supply input circuit 30 includes a first diode D01 and asecond diode D02. An anode of the first diode D01 is connected to thepositive electrode of the battery 20 via a switching element T01. In thepresent embodiment, the switching element T01 is, for example, ap-channel metal-oxide-semiconductor field-effect transistor (MOSFET).The anode of the first diode D01 is connected to a drain of theswitching element T01. A source of the switching element T01 isconnected to the positive electrode of the battery 20. A gate of theswitching element T01 is connected to the battery control circuit 23.

An anode of the second diode D02 is connected to the Vcc/TFB terminal18. A cathode of the first diode D01 and a cathode of the second diodeD02 are connected to each other and also connected to an input terminalof the power-supply circuit 31.

The battery control circuit 23 determines whether the battery 20 is inan over-discharge state based on the battery voltage information inputfrom the voltage detection circuit 32. The battery control circuit 23may determine whether the battery 20 is in an over-discharge state inany manner. For example, the battery control circuit 23 may determinethat the battery 20 is in an over-discharge state if the battery voltagevalue indicated by the battery voltage information is lower than aspecified voltage lower limit.

During a period in which the battery 20 is not in an over-dischargestate, the battery control circuit 23 turns on the switching element T01to thereby supply the battery power to the power-supply circuit 31 viathe switching element T01 and the first diode D01. If the batterycontrol circuit 23 determines that the battery 20 is in anover-discharge state, the battery control circuit 23 turns off theswitching element T01 to thereby interrupt supply of the battery powerto the power-supply circuit 31.

The voltage detection circuit 32 may output information indicating avoltage value of each of the cells in the battery 20 to the batterycontrol circuit 23. In this case, the battery control circuit 23 maydetermine that the battery 20 is in an over-discharge state if thevoltage value of at least one cell is lower than a specified cellvoltage lower limit.

Alternatively, instead of the battery control circuit 23, the voltagedetection circuit 32 may determine that the battery 20 is in anover-discharge state if the battery voltage value is lower than thespecified voltage lower limit, or if the voltage value of at least onecell is lower than the specified cell voltage lower limit. In this case,the battery control circuit 23 may turn off the switching element T01 inresponse to determination of the over-discharge state by the voltagedetection circuit 32.

The power-supply circuit 31 generates a control voltage Vc of a directcurrent based on an input voltage of a direct current to thepower-supply circuit 31. The control voltage Vc is lower than the inputvoltage. The control voltage Vc is supplied to relevant portions withinthe battery pack 10, including the battery control circuit 23.

If the battery 20 is not in an over-discharge state, the battery voltageis input to the power-supply circuit 31 via the switching element T01and the first diode D01. In this case, the power-supply circuit 31converts the battery voltage into the control voltage Vc and outputs thecontrol voltage Vc.

In response to the battery 20 entering an over-discharge state, thebattery control circuit 23 sets the battery control circuit 23 itself toa shutdown mode. Specifically, the battery control circuit 23 turns offthe switching element T01 to interrupt input of the battery voltage tothe power-supply circuit 31. As a result, the power-supply circuit 31stops output of the control voltage Vc, thus stopping operation of thebattery control circuit 23.

The battery control circuit 23 in the shutdown mode cannot turn on theswitching element T01 by itself. Attachment of the battery pack 10 tothe charger 40 in operation disengages the shutdown mode.

In response to attachment of the battery pack 10 to the charger 40 inoperation, as shown in FIG. 5, a first power supply voltage Vcc to bedescribed below is input from the charger 40 to the Vcc/TFB terminal 18.The first power supply voltage Vcc input to the Vcc/TFB terminal 18 isinput to the power-supply circuit 31 via the second diode D02 shown inFIG. 1. In response to input of the first power supply voltage Vcc tothe power-supply circuit 31 during the shutdown mode of the batterycontrol circuit 23, the power-supply circuit 31 generates the controlvoltage Vc based on the first power supply voltage Vcc (i.e., convertsthe first power supply voltage Vcc into the control voltage Vc). Supplyof the control voltage Vc from the power-supply circuit 31 to thebattery control circuit 23 activates the battery control circuit 23. Thebattery control circuit 23 activated from the shutdown mode turns on theswitching element T01 in response to the battery voltage value reachingthe voltage lower limit by charging of the battery 20. As a result, thebattery voltage is input to the power-supply circuit 31, and it becomespossible for the power-supply circuit 31 to generate the control voltageVc based on the battery voltage.

The power-supply circuit 31 may be configured in any manner. Thepower-supply circuit 31 may include a switching regulator, and may beconfigured to convert the input voltage into the control voltage Vc withthe switching regulator. Alternatively, the power-supply circuit 31 mayinclude a linear regulator, and may be configured to convert the inputvoltage into the control voltage Vc with the linear regulator. Thecontrol voltage Vc may have any voltage value. The first power supplyvoltage Vcc may have any voltage value. In the present embodiment, thepower-supply circuit 31 includes, for example, a linear regulator; thefirst power supply voltage Vcc is, for example, 5 V; and the controlvoltage Vc is, for example, 3.3 V.

The first power supply voltage Vcc input from the charger 40 to theVcc/TFB terminal 18 is further input to the attachment detection circuit28. In response to attachment of the battery pack 10 to the workingmachine body 200, a body detection voltage is input to the Vcc/TFBterminal 18 from the working machine body 200.

The attachment detection circuit 28 is provided in order for the batterycontrol circuit 23 to detect that the battery pack 10 is attached to thecharger 40 or to the working machine body 200. As shown in FIGS. 1 and5, the attachment detection circuit 28 includes resistors R01, R02, andR03, a Zener diode D03, a capacitor C01, and a switching element T02. Inthe present embodiment, the switching element T02 is, for example, ann-channel MOSFET.

A first terminal of the resistor R01 is connected to the Vcc/TFBterminal 18, and a second terminal of the resistor R01 is connected to agate of the switching element T02. A source of the switching element T02is connected to a ground line having a reference potential in thebattery pack 10. The Zener diode D03, the capacitor C01, and theresistor R02 are each connected between the gate of the switchingelement T02 and the ground line. A drain of the switching element T02 isconnected to a first terminal of the resistor R03 and to the batterycontrol circuit 23. The control voltage Vc is input to a second terminalof the resistor R03.

If the battery pack 10 is attached to neither the charger 40 nor theworking machine body 200, the switching element T02 is turned off. Inthis case, a non-attachment signal (specifically, a HIGH-level signal)is input from the attachment detection circuit 28 to the battery controlcircuit 23.

As shown in FIG. 5, in response to attachment of the battery pack 10 tothe charger 40, the first power supply voltage Vcc is input from thecharger 40 to the attachment detection circuit 28 via the Vcc/TFBterminal 18, and the switching element T02 is turned on. In this case,an attachment signal (specifically, a LOW-level signal) is output fromthe attachment detection circuit 28 to the battery control circuit 23.

In response to attachment of the battery pack 10 to the working machinebody 200, the body detection voltage is input from the working machinebody 200 to the attachment detection circuit 28 via the Vcc/TFB terminal18, and the switching element T02 is turned on. In this case, theabove-described attachment signal is input from the attachment detectioncircuit 28 to the battery control circuit 23.

The battery control circuit 23 can detect whether the battery pack 10 isnot attached to anything or attached to the charger 40 or to the workingmachine body 200, based on the non-attachment signal or the attachmentsignal, respectively, input from the attachment detection circuit 28.

The battery control circuit 23 has a serial communication function.Specifically, the battery control circuit 23 transmits transmission datafrom the Tx terminal 15 via the Tx circuit 25. Further, the batterycontrol circuit 23 receives reception data input to the Rx terminal 17via the Rx circuit 27.

The transmission data is represented by a binary signal of a HIGH levelor a LOW level. In the Tx circuit 25, an input impedance from theperspective of the Tx terminal 15 varies to a low impedance or a highimpedance according to a logic level of a signal input from the batterycontrol circuit 23. The low impedance refers to, for example, animpedance lower than or equal to a first threshold, and the highimpedance refers to, for example, an impedance higher than a secondthreshold. The second threshold may be the same as the first threshold,or may be larger than the first threshold.

While the transmission data is not transmitted, the battery controlcircuit 23 continuously outputs a HIGH-level signal indicating atransmission standby state to the Tx circuit 25. In the transmissionstandby state, the input impedance of the Tx terminal 15 is a lowimpedance (e.g., approximately 10.5 kΩ). The battery control circuit 23outputs a HIGH-level signal or a LOW-level signal to the Tx circuit 25based on details of the transmission data. If a LOW-level signal isoutput from the battery control circuit 23 to the Tx circuit 25, theinput impedance of the Tx terminal 15 becomes a high impedance.

An input impedance of the Vcc/TFB terminal 18, namely, an inputimpedance of the attachment detection circuit 28 from the perspective ofthe Vcc/TFB terminal 18, is a high impedance (e.g., approximately 9.4MΩ, see FIG. 5) in the present embodiment.

The reception data input to the Rx terminal 17 of the battery pack 10 isrepresented by a binary signal of a HIGH level or a LOW level. As shownin FIG. 6, the Rx circuit 27 in the battery pack 10 includes resistorsR08, R09, R10, and R11, a capacitor C04, and a switching element T05. Inthe present embodiment, the switching element T05 is, for example, anNPN-type bipolar transistor.

A first terminal of the resistor R08 is connected to the Rx terminal 17,and a second terminal of the resistor R08 is connected to a firstterminal of the resistor R09. A second terminal of the resistor R09 isconnected to a base of the switching element T05. An emitter of theswitching element T05 is connected to the ground line. The resistor R10is connected between the base and the emitter of the switching elementT05. The capacitor C04 is connected between the second terminal of theresistor R08 and the ground line. A collector of the switching elementT05 is connected to a first terminal of the resistor R11 and to thebattery control circuit 23. The control voltage Vc is input to a secondterminal of the resistor R11.

An input impedance of the Rx terminal 17, namely, an input impedance ofthe Rx circuit 27 from the perspective of the Rx terminal 17, is a lowimpedance (e.g., approximately 8 kΩ) in the present embodiment,regardless of whether the switching element T05 is ON or OFF.

In response to input of a LOW-level signal to the Rx terminal 17, theswitching element T05 in the Rx circuit 27 is turned off. In this case,a HIGH-level signal is input from the Rx circuit 27 to the batterycontrol circuit 23. In response to input of a HIGH-level signal to theRx terminal 17, the switching element T05 is turned on. In this case, aLOW-level signal is input from the Rx circuit 27 to the battery controlcircuit 23. The battery control circuit 23 recognizes details of thereception data based on a logic level of the signal input from the Rxcircuit 27.

The battery control circuit 23 outputs a LOW-level signal or aHIGH-level signal to the BD/TS circuit 26 depending on whether thebattery 20 is in an over-discharge state, to thereby change an inputimpedance of the BD/TS terminal 16, namely, an input impedance of theBD/TS circuit 26 from the perspective of the BD/TS terminal 16, to afirst impedance or a second impedance. The first impedance and thesecond impedance are each a high impedance; however, the secondimpedance is higher than the first impedance.

Specifically, if the battery 20 is not in an over-discharge state, thebattery control circuit 23 outputs a HIGH-level signal to the BD/TScircuit 26, to thereby set the input impedance of the BD/TS terminal 16to the first impedance (e.g., approximately 6.2 MΩ). If the battery 20is in an over-discharge state, the battery control circuit 23 outputs aLOW-level signal to the BD/TS circuit 26, to thereby set the inputimpedance of the BD/TS terminal 16 to the second impedance.

A manipulation signal is input to the TD terminal 19 from the workingmachine body 200. This manipulation signal is a binary signal of a HIGHlevel or a LOW level, and indicates whether a manipulator 217 (see FIG.3) to be described later is manipulated by a user of the electricworking machine. The manipulation signal is, for example, a LOW level ifthe manipulator 217 is not manipulated, and is, for example, a HIGHlevel if the manipulator 217 is manipulated.

If the manipulation signal of a LOW level is input to the TD terminal19, the TD input circuit 29 outputs, to the battery control circuit 23,manipulation information (e.g., a HIGH-level signal) indicating that themanipulator 217 is not manipulated. If the manipulation signal of a HIGHlevel is input to the TD terminal 19, the TD input circuit 29 outputs,to the battery control circuit 23, manipulation information (e.g., aLOW-level signal) indicating that the manipulator 217 is manipulated.The battery control circuit 23 can recognize whether the manipulator 217is manipulated, based on the manipulation information input from the TDinput circuit 29.

An input impedance of the TD terminal 19, namely, an input impedance ofthe TD input circuit 29 from the perspective of the TD terminal 19, is ahigh impedance (e.g., approximately 110 kΩ) in the present embodiment.

The battery control circuit 23 monitors whether the battery pack 10 isin a specific improper state, and outputs a permission command or aprohibition command to the ES output circuit 24 depending on a result ofthe monitoring. The specific improper state may be, for example, a statein which discharge from the battery 20 and charging of the battery 20should be stopped.

The battery control circuit 23 may determine whether the battery pack 10is in the specific improper state in any manner. The battery controlcircuit 23 may determine whether the battery pack 10 is in the specificimproper state based on, for example, at least the battery voltageinformation, the discharge current information, the charging currentinformation, or the temperature information, which are described above.

The specific improper state may be any state. The battery controlcircuit 23 may determine that the battery pack 10 is in the specificimproper state if, for example, the battery 20 is in an over-dischargestate or if the over-discharge state continues for a specified period oftime. The battery control circuit 23 may determine that the battery pack10 is in the specific improper state if, for example, the value ofdischarge current from the battery 20 exceeds a specified current upperlimit or if a state in which the value of discharge current from thebattery 20 is higher than the current upper limit continues for aspecified period of time. The battery control circuit 23 may determinethat the battery pack 10 is in the specific improper state if, forexample, a temperature of the battery 20 exceeds a specified temperatureupper limit or if a state in which the temperature is higher than thetemperature upper limit continues for a specified period of time.

If the battery pack 10 is not in the specific improper state, thebattery control circuit 23 outputs the permission command (e.g., aHIGH-level signal in the present embodiment) to the ES output circuit24. If the battery pack 10 is in the specific improper state, thebattery control circuit 23 outputs the prohibition command (e.g., aLOW-level signal in the present embodiment) to the ES output circuit 24.

As shown in FIG. 4, the ES output circuit 24 of the present embodimentincludes resistors R04, R05, R06, and R07, capacitors C02 and C03, Zenerdiodes D04 and D05, and a switching element T03. In the presentembodiment, the switching element T03 is, for example, an n-channelMOSFET.

Input from the battery control circuit 23 to a first terminal of theresistor R07 is the permission command (HIGH level) or the prohibitioncommand (LOW level). A second terminal of the resistor R07 is connectedto a gate of the switching element T03. A source of the switchingelement T03 is connected to the ground line. The resistor R06 and thecapacitor C03 are each connected between the gate of the switchingelement T03 and the ground line. A drain of the switching element T03 isconnected to a first terminal of the resistor R05 and to a cathode ofthe Zener diode D04. An anode of the Zener diode D04 is connected to acathode of the Zener diode D05, and an anode of the Zener diode D05 isconnected to the ground line. A second terminal of the resistor R05 isconnected to a first terminal of the resistor R04. A second terminal ofthe resistor R04 is connected to the ES terminal 14. The capacitor C02is connected between the first terminal of the resistor R04 and theground line.

In response to input of the permission command (HIGH level) from thebattery control circuit 23 to the ES output circuit 24 configured asabove, the switching element T03 is turned on in the ES output circuit24. As a result, an input impedance of the ES terminal 14, namely, aninput impedance of the ES output circuit 24 from the perspective of theES terminal 14, becomes a low impedance (e.g., approximately 10.5 kΩ).In other words, a logic level of the ES terminal 14 becomes a LOW level.

On the other hand, in response to input of the prohibition command (LOWlevel) from the battery control circuit 23 to the ES output circuit 24,the switching element T03 is turned off in the ES output circuit 24. Asa result, the input impedance of the ES terminal 14 becomes a highimpedance.

(3) Configuration of Charger

As shown in FIG. 2, the charger 40 includes a positive terminal 41, anegative terminal 42, a center terminal 43, an ES terminal 44, an Rxterminal 45, a BD terminal 46, a Tx terminal 47, and a Vcc terminal 48.

In response to attachment of the battery pack 10 to the charger 40, theabove-described terminals of the charger 40 are connected to theterminals of the battery pack 10 as follows. The positive terminal 41 isconnected to the positive terminal 11 of the battery pack 10. Thenegative terminal 42 is connected to the negative terminal 12 of thebattery pack 10. The center terminal 43 is connected to the centerterminal 13 of the battery pack 10. The ES terminal 44 is connected tothe ES terminal 14 of the battery pack 10. The Rx terminal 45 isconnected to the Tx terminal 15 of the battery pack 10. The BD terminal46 is connected to the BD/TS terminal 16 of the battery pack 10. The Txterminal 47 is connected to the Rx terminal 17 of the battery pack 10.The Vcc terminal 48 is connected to the Vcc/TFB terminal 18 of thebattery pack 10.

The charger 40 includes no counterpart terminal to the TD terminal 19 ofthe battery pack 10. Thus, in response to attachment of the battery pack10 to the charger 40, the TD terminal 19 of the battery pack 10 is notelectrically connected to the charger 40 and is electrically open.

The charger 40 further includes a power plug 50, a rectifier circuit 51,a power factor correction (PFC) circuit 52, a smoothing circuit 53, amain converter 54, a positive electrode line 55, a negative electrodeline 56, a cell group switching circuit 57, a line switch circuit 58, aswitch drive circuit 59, a charging control circuit 60, a currentdetection circuit 61, a differential amplifier circuit 62, a low-passfilter 63, and an output setting circuit 64.

The power plug 50 is configured to be connected to an alternating (AC)power source, such as a commercial power source that supplies a voltageof, for example, AC 100 V, and to receive an AC power from the AC powersource. The rectifier circuit 51 rectifies (e.g., full-wave rectifies)the AC power input from the power plug 50, and outputs the rectifiedelectric power. The PFC circuit 52 improves a power factor of the ACpower input to the rectifier circuit 51. The smoothing circuit 53smoothes the electric power output from the PFC circuit 52. Thesmoothing circuit 53 of the present embodiment includes a capacitor tosmooth the electric power input to the smoothing circuit 53. One of thepurposes of providing the PFC circuit 52 is to make the power factor ofthe AC power closer to 1 by bringing the waveform of the AC current ofthe AC power input from the power plug 50 closer to a sine wave.

The main converter 54 converts a direct (DC) power smoothed by thesmoothing circuit 53 into the charging power having a voltage suitablefor charging the battery 20. In the present embodiment, the mainconverter 54 includes, for example, an insulated step-down switchingpower supply circuit. The main converter 54 is operated in accordancewith a switching command input from the output setting circuit 64 to bedescribed below, and generates the charging power.

The main converter 54 is connected to a first end of the positiveelectrode line 55 and to a first end of the negative electrode line 56.The charging power is supplied from the main converter 54 to the batterypack 10 via the positive electrode line 55 and the negative electrodeline 56.

A second end of the positive electrode line 55 and a second end of thenegative electrode line 56 are connected to the cell group switchingcircuit 57. The cell group switching circuit 57 includes a positiveelectrode switch 57 a and a negative electrode switch 57 b, which areoperated in association with each other. The positive electrode switch57 a and the negative electrode switch 57 b are C-contact type switches.The second end of the positive electrode line 55 is connected to acommon terminal of the positive electrode switch 57 a, and the secondend of the negative electrode line 56 is connected to a common terminalof the negative electrode switch 57 b.

A first terminal of the positive electrode switch 57 a is connected tothe positive terminal 41. A second terminal of the positive electrodeswitch 57 a is connected to the center terminal 43. A first terminal ofthe negative electrode switch 57 b is connected to the center terminal43. A second terminal of the negative electrode switch 57 b is connectedto the negative terminal 42.

The cell group switching circuit 57 is switched to a first connectionstate or a second connection state in accordance with a switchingcommand input from the charging control circuit 60. In the firstconnection state, the common terminal of the positive electrode switch57 a is connected to the first terminal of the positive electrode switch57 a, and the common terminal of the negative electrode switch 57 b isconnected to the first terminal of the negative electrode switch 57 b.In the second connection state, the common terminal of the positiveelectrode switch 57 a is connected to the second terminal of thepositive electrode switch 57 a, and the common terminal of the negativeelectrode switch 57 b is connected to the second terminal of thenegative electrode switch 57 b.

In the present embodiment, the battery 20 is charged while the cellgroup switching circuit 57 is alternately switched between the firstconnection state and the second connection state. Specifically, thefirst cell group 21 is charged in the first connection state, and thesecond cell group 22 is charged in the second connection state.

The line switch circuit 58 is provided on the positive electrode line 55to establish (complete) or interrupt the positive electrode line 55. Theline switch circuit 58 is turned on or off by the charging controlcircuit 60 via the switch drive circuit 59. In response to turning-on ofthe line switch circuit 58, the positive electrode line 55 isestablished, thus allowing supply of the charging power to the batterypack 10. In response to turning-off of the line switch circuit 58, thepositive electrode line 55 is interrupted, thus supplying no chargingpower to the battery pack 10. The line switch circuit 58 may beconfigured in any manner. The line switch circuit 58 may include, forexample, at least one switching element (e.g., MOSFET) configured toestablish or interrupt the positive electrode line 55.

The current detection circuit 61 is provided on the negative electrodeline 56. The current detection circuit 61 outputs a current detectionsignal Si indicating a value of the electric current flowing through thenegative electrode line 56. In the present embodiment, the currentdetection signal Si has a voltage value according to the value of theelectric current. The current detection circuit 61 may include, forexample, a shunt resistor (not shown) arranged on the negative electrodeline 56, and may be configured to output the current detection signal Siaccording to a voltage across the shunt resistor.

The current detection signal Si is input to the charging control circuit60 and to the differential amplifier circuit 62. The charging controlcircuit 60 generates a pulse-width modulation (PWM) signal according tothe above-described charging current command value acquired from thebattery pack 10 through data communication with the battery pack 10,namely, generates a pulse signal having a duty ratio according to thecharging current command value, and outputs the generated PWM signal tothe low-pass filter 63. The low-pass filter 63 smoothes the PWM signalinput from the charging control circuit 60, and outputs the smoothed PWMsignal to the differential amplifier circuit 62.

The differential amplifier circuit 62 outputs a differential signal Difaccording to a difference between a voltage value of the PWM signalsmoothed by the low-pass filter 63 and the voltage value of the currentdetection signal Si. The differential signal Dif is input to the outputsetting circuit 64, and is output, as the above-described switchingcommand, to the main converter 54 via the output setting circuit 64. Themain converter 54 generates the charging power based on the differentialsignal Dif input as the switching command so that the differentialsignal Dif becomes zero, namely, so that the value of the chargingcurrent output from the main converter 54 becomes equal to a currentvalue indicated by the charging current command value.

The output setting circuit 64 is supplied with a charging voltage upperlimit from the charging control circuit 60, and also supplied with avoltage value of the positive electrode line 55 (specifically, a voltagevalue between the main converter 54 and the line switch circuit 58). Ifthe voltage value of the positive electrode line 55 is lower than orequal to the charging voltage upper limit, the output setting circuit 64outputs the differential signal Dif to the main converter 54 as theswitching command. If the voltage value of the positive electrode line55 is higher than the charging voltage upper limit, the output settingcircuit 64 outputs the switching command for reducing the chargingpower, to thereby reduce the voltage value of the charging power outputfrom the main converter 54.

Provided between the main converter 54 and the line switch circuit 58 onthe positive electrode line 55 is a rectifier circuit 65, a smoothingcircuit 66, and a discharge circuit 67.

Since the main converter 54 of the present embodiment is insulated type,the charging power output from the main converter 54 is an AC power. Therectifier circuit 65 rectifies the charging power in the form of the ACpower output from the main converter 54.

The smoothing circuit 66 includes a capacitor C41. A first terminal ofthe capacitor C41 is connected to the positive electrode line 55, and asecond terminal of the capacitor C41 is connected to the negativeelectrode line 56. The smoothing circuit 66 smoothes the charging powerrectified by the rectifier circuit 65.

The discharge circuit 67 discharges electric charges charged in thecapacitor C41. The discharge circuit 67 includes resistors R41 and R42,and a switching element T41. The switching element T41 is, for example,an NPN-type bipolar transistor. A base of the switching element T41 isconnected to the charging control circuit 60 via the resistor R42. Anemitter of the switching element T41 is connected to the negativeelectrode line 56 (more specifically, between the main converter 54 andthe current detection circuit 61). A collector of the switching elementT41 is connected to the positive electrode line 55 via the resistor R41.Such a configuration allows discharge of the electric charges in thecapacitor C41, in response to turning-on of the switching element T41 bythe charging control circuit 60.

On the positive electrode line 55, a diode D41 is provided between theline switch circuit 58 and the cell group switching circuit 57. Thediode D41 inhibits a reverse flow of the current from the positiveterminal 41 or the center terminal 43 to the line switch circuit 58.

The charger 40 further includes a sub-converter 68. The sub-converter 68converts the direct (DC) power smoothed by the smoothing circuit 53 intoa power-supply power. The power-supply power has a voltage valuedifferent from a value of voltage output from the main converter 54. Inthe present embodiment, the sub-converter 68 includes, for example, aninsulated step-down switching power supply circuit. Thus, thepower-supply power output from the sub-converter 68 is an AC power.

The power-supply power output from the sub-converter 68 is rectified bya rectifier circuit 69 and smoothed by a smoothing circuit 70. A secondpower-supply voltage VD, which is a DC voltage output from the smoothingcircuit 70, is used for a fan 90, a buzzer 93, and so on, to bedescribed below.

The power-supply power output from the sub-converter 68 is furtherrectified by a rectifier circuit 71 and smoothed by a smoothing circuit72. A DC voltage output from the smoothing circuit 72 is input to apower-supply circuit 73. The power-supply circuit 73 converts the DCvoltage input from the smoothing circuit 72 into the first power supplyvoltage Vcc. The first power supply voltage Vcc is a DC voltage lowerthan the DC voltage input from the smoothing circuit 72. The first powersupply voltage Vcc is used for relevant portions in the charger 40,including the charging control circuit 60.

The charger 40 further includes five terminal protection circuits 84,85, 86, 87, and 88, an ES input circuit 74, an Rx circuit 75, a BD inputcircuit 76, and a Tx circuit 77. The terminal protection circuits 84,85, 86, 87, and 88 have the same configuration.

The ES input circuit 74 is connected to the ES terminal 44 via theterminal protection circuit 84. The Rx circuit 75 is connected to the Rxterminal 45 via the terminal protection circuit 85. The BD input circuit76 is connected to the BD terminal 46 via the terminal protectioncircuit 86. The Tx circuit 77 is connected to the Tx terminal 47 via theterminal protection circuit 87.

The terminal protection circuit 88 is connected to the Vcc terminal 48.The first power supply voltage Vcc is input to the terminal protectioncircuit 88. That is, the first power supply voltage Vcc can be outputfrom the charger 40 via the terminal protection circuit 88 and the Vccterminal 48. Thus, in response to attachment of the battery pack 10 tothe charger 40, the first power supply voltage Vcc is input from the Vccterminal 48 of the charger 40 to the Vcc/TFB terminal 18 of the batterypack 10.

The configuration of the terminal protection circuits 84, 85, 86, 87,and 88 will be described with reference to FIG. 4, with the terminalprotection circuit 84 as an example. The terminal protection circuit 88is shown in FIG. 5, and the terminal protection circuit 87 is shown inFIG. 6.

As shown in FIG. 4, the terminal protection circuit 84 includes twoZener diodes D43 and D44, a diode D45, and a varistor 96. A cathode ofthe Zener diode D43 is connected to the ES terminal 44, and an anode ofthe Zener diode D43 is connected to a cathode of the Zener diode D44. Ananode of the Zener diode D44 is connected to a ground line via thevaristor 96. A cathode of the diode D45 is connected to the ES terminal44. An anode of the diode D45 is connected to the ES input circuit 74.

The diode D45 inhibits undesirable influence from being exerted on theinside of the charger 40 in a case where an external connection terminal(the ES terminal 44 in FIG. 4) connected to the diode D45 is shorted toanother external connection terminal (e.g., the Rx terminal 45, the BDterminal 46, the Tx terminal 47, and the Vcc terminal 48).

The Zener diodes D43 and D44 are provided to protect the relevantexternal connection terminal (the ES terminal 44 in FIG. 4) fromovervoltage. In the present embodiment, the Zener diodes D43 and D44connected to each other in series are used because the rated voltagevalue of the battery 20 is a relatively high value (e.g., 57.6 V). Ifthe rated voltage value of the battery 20 is low, a single Zener diodemay be used.

The varistor 96 is provided to inhibit an unnecessary loop current fromflowing between the charger 40 and the battery pack 10 during chargingof the battery 20. In the present embodiment, as described above, thebattery 20 is charged while the cell group switching circuit 57 isalternately switched between the first connection state and the secondconnection state.

Here, in the case where the cell group switching circuit 57 is in thefirst connection state, absence of the varistor 96 may lead togeneration of the loop current as follows. Specifically, such loopcurrent flows from the positive electrode of the second cell group 22 tothe negative electrode of the second cell group 22 via the centerterminal 13 of the battery pack 10, the center terminal 43 of thecharger 40, the negative electrode switch 57 b in the cell groupswitching circuit 57, the ground line of the charger 40, the Zenerdiodes D43 and D44 in the terminal protection circuit 84, the ESterminal 44 of the charger 40, the ES terminal 14 and the ES outputcircuit 24 in the battery pack 10, and the ground line of the batterypack 10.

A factor of generation of such loop current is that, in the firstconnection state, the potential of the ground line of the charger 40becomes equal to the potential of the positive electrode of the secondcell group 22 in the battery pack 10. Also in the external connectionterminal other than the ES terminal 44, a loop current may be generateddue to a similar factor. Thus, in the present embodiment, the varistor96 is provided in the terminal protection circuits 84 to 88 to inhibitgeneration of the loop current described above.

As shown in FIG. 4, the ES input circuit 74 includes a first inputcircuit 74 a and a second input circuit 74 b. The first input circuit 74a includes resistors R43 and R44, and a switching element T42. Theswitching element T42 is, for example, a PNP-type bipolar transistor. Afirst terminal of the resistor R43 is connected to the terminalprotection circuit 84 (specifically, the anode of the diode D45). Asecond terminal of the resistor R43 is connected to a base of theswitching element T42. The first power supply voltage Vcc is applied toan emitter of the switching element T42. The resistor R44 is connectedbetween the emitter and the base of the switching element T42.

The second input circuit 74 b includes resistors R45, R46, and R47, anda switching element T43. The switching element T43 is, for example, anNPN-type bipolar transistor. A first terminal of the resistor R45 isconnected to a collector of the switching element T42 in the first inputcircuit 74 a. A second terminal of the resistor R45 is connected to abase of the switching element T43. An emitter of the switching elementT43 is connected to the ground line. The resistor R46 is connectedbetween the emitter and the base of the switching element T43. The firstpower supply voltage Vcc is applied to a collector of the switchingelement T43 via the resistor R47.

The voltage of the collector of the switching element T43 is output tothe charging control circuit 60 and to the switch drive circuit 59 as anES signal. A resistance value of the resistor R43 is, for example,approximately 2 kΩ, and a resistance value of the resistor R44 is, forexample, approximately 20 kΩ.

In the battery pack 10, if the permission command is output from thebattery control circuit 23 to the ES output circuit 24, the inputimpedance of the ES terminal 14 of the battery pack 10 becomes a lowimpedance as described above. Thus, in the ES input circuit 74 of thecharger 40, the switching elements T42 and T43 are each turned on, andthe ES signal of a LOW level (hereinafter referred to as an “ESpermission signal”) is output.

In the battery pack 10, if the prohibition command is output from thebattery control circuit 23 to the ES output circuit 24, the inputimpedance of the ES terminal 14 of the battery pack 10 becomes a highimpedance as described above. Thus, in the ES input circuit 74 of thecharger 40, the switching elements T42 and T43 are each turned off, andthe ES signal of a HIGH level (hereinafter referred to as an “ESprohibition signal”) is output.

If the ES permission signal is input from the ES input circuit 74 to thecharging control circuit 60, the charging control circuit 60 charges thebattery 20 while performing data communication with the battery pack 10.Specifically, the charging control circuit 60 turns on the line switchcircuit 58 via the switch drive circuit 59 and outputs theabove-described PWM signal to cause the main converter 54 to generatethe charging power, to thereby supply the charging power to the batterypack 10.

If the ES prohibition signal is input from the ES input circuit 74 tothe charging control circuit 60, the charging control circuit 60 stopscharging of the battery 20. Specifically, the charging control circuit60 stops output of the PWM signal and turns off the line switch circuit58 via the switch drive circuit 59.

If the ES permission signal is input from the ES input circuit 74 to theswitch drive circuit 59, the switch drive circuit 59 turns on or off theline switch circuit 58 in accordance with a switch drive command inputfrom the charging control circuit 60. That is, while the ES permissionsignal is input, control of the line switch circuit 58 by the chargingcontrol circuit 60 is enabled.

If the ES prohibition signal is input from the ES input circuit 74 tothe switch drive circuit 59, the switch drive circuit 59 forcibly turnsoff the line switch circuit 58 independently of the switch drive commandinput from the charging control circuit 60. That is, while the ESprohibition signal is input, the control of the line switch circuit 58by the charging control circuit 60 is disabled. The switch drive circuit59 is configured to turn on or off the line switch circuit 58 byhardware processing without performing software processing.

If the ES prohibition signal is output from the ES input circuit 74during charging, the charging control circuit 60 performs softwareprocessing for turning off the line switch circuit 58. In this case,there is a certain time lag between output of the ES prohibition signaland output of the switch drive command for turning off the line switchcircuit 58 from the charging control circuit 60 to the switch drivecircuit 59.

Thus, if the ES prohibition signal is output from the ES input circuit74, the ES prohibition signal is input to the switch drive circuit 59prior to input thereto of the switch drive command for turning off theline switch circuit 58 from the charging control circuit 60. Due to sucha configuration, in the charger 40 of the present embodiment, if the ESprohibition signal is output from the ES input circuit 74, the lineswitch circuit 58 can be promptly turned off by hardware processing.

The Rx circuit 75 receives, via the Rx terminal 45, the transmissiondata transmitted from the battery pack 10, and relays the received datato the charging control circuit 60. The charging control circuit 60acquires, via the Rx circuit 75, the transmission data received from thebattery pack 10.

The BD input circuit 76 outputs, to the charging control circuit 60, asignal according to the impedance of the BD/TS terminal 16 of thebattery pack 10 connected to the BD terminal 46. The charging controlcircuit 60 determines whether the battery pack 10 is attached to thecharger 40, based on the signal input from the BD input circuit 76.Specifically, if the input impedance of the BD/TS terminal 16 of thebattery pack 10 is the above-described first impedance, the chargingcontrol circuit 60 determines that the battery pack 10 is attached tothe charger 40. If the input impedance of the BD/TS terminal 16 of thebattery pack 10 is the above-described second impedance, the chargingcontrol circuit 60 determines that the battery pack 10 is not attachedto the charger 40.

The Tx circuit 77 relays the transmission data output from the chargingcontrol circuit 60 to the battery pack 10. As shown in FIG. 6, the Txcircuit 77 includes resistors R48, R49, and R50, and a switching elementT44. The switching element T44 is, for example, a PNP-type bipolartransistor.

A first terminal of the resistor R48 is connected to the terminalprotection circuit 87 (specifically, the anode of the diode D45). Asecond terminal of the resistor R48 is connected to a collector of theswitching element T44. The first power supply voltage Vcc is applied toan emitter of the switching element T44. The resistor R49 is connectedbetween the emitter and a base of the switching element T44. A firstterminal of the resistor R50 is connected to the base of the switchingelement T44. The transmission data is input to a second terminal of theresistor R50 from the charging control circuit 60. The transmission dataoutput from the charging control circuit 60 is represented by a binarysignal of a HIGH level or a LOW level.

The charger 40 further includes the fan 90, a locking detection circuit91, and a temperature detection circuit 92. The fan 90 is rotated withthe second power-supply voltage VD to supply cooling air toheat-generating parts in the charger 40 (e.g., a not-shown switchingelement in the main converter 54). The charging control circuit 60drives the fan 90 continuously or intermittently during supply of thecharging power to the battery pack 10.

The locking detection circuit 91 detects locking of the fan 90. Iflocking of the fan 90 is detected by the locking detection circuit 91during driving of the fan 90, the charging control circuit 60 decreasesthe value of the current to be output from the main converter 54, thusinhibiting overheating of the switching element in the main converter54.

The temperature detection circuit 92 detects a temperature of theswitching element in the main converter 54. The charging control circuit60 controls the value of the charging current based on the temperaturedetected by the temperature detection circuit 92 (i.e., controls the PWMsignal). For example, if the detected temperature is higher than orequal to a temperature threshold, the charging control circuit 60generates a PWM signal with a duty ratio lower than a duty ratioaccording to the charging current command value from the battery pack 10to reduce the charging current.

The charger 40 further includes the buzzer 93 and an attenuator 94. Thesecond power-supply voltage VD is input to the buzzer 93. Further, thebattery power is input to the buzzer 93 from the battery pack 10attached to the charger 40 via a diode D42 and the attenuator 94. Theattenuator 94 steps down the battery voltage and outputs thestepped-down battery voltage to the buzzer 93. The buzzer 93 is operatedwith the second power-supply voltage VD or the battery power. Thecharging control circuit 60 activates the buzzer 93 in response tooccurrence of various events, such as completion of charging of thebattery 20, any malfunction, and so on. This enables the user to beaware of occurrence of such various events in an auditory manner.

In the charger 40 configured as above, in response to detection ofattachment of the battery pack 10 to the charger 40 by the signal inputfrom the BD input circuit 76, the charging control circuit 60 executes acharging control process for charging the battery 20. Specifically, thecharging control circuit 60 performs serial data communication with thebattery pack 10 to acquire various information including theabove-described charging current command value. If charging of thebattery 20 is necessary, the charging control circuit 60 turns on theline switch circuit 58 and outputs the PWM signal according to thecharging current command value, to thereby initiate charging of thebattery 20. As described above, the charging control circuit 60 performscharging of the battery 20 while alternately switching the cell groupswitching circuit 57 between the first connection state and the secondconnection state. That is, the charging control circuit 60 performscharging of the first cell group 21 and charging of the second cellgroup 22 in a parallel manner. The charging control circuit 60 mayperform switching between the first connection state and the secondconnection state at any time point, for example, at regular intervals(e.g., every one minute).

Before initiating supply of the charging power to the battery pack 10(specifically, before turning on the line switch circuit 58), thecharging control circuit 60 discharge the electric charges from thecapacitor C41 in the smoothing circuit 66 by controlling the dischargecircuit 67. Specifically, the charging control circuit 60 turns on theswitching element T41 in the discharge circuit 67 and keeps theswitching element T41 ON for a specified period of time. The main reasonfor providing the discharge circuit 67 is to inhibit a large currentfrom flowing from the capacitor C41 to the battery pack 10 at the startof charging.

(4) Configuration of Working Machine Body

As shown in FIG. 3, the working machine body 200 includes a positiveterminal 201, a negative terminal 202, an ES terminal 204, an Rxterminal 205, a TS terminal 206, a Tx terminal 207, a TFB terminal 208,and a TD terminal 209.

In response to attachment of the battery pack 10 to the working machinebody 200, the above-described terminals of the working machine body 200are connected to the terminals of the battery pack 10 as follows. Thepositive terminal 201 is connected to the positive terminal 11 of thebattery pack 10. The negative terminal 202 is connected to the negativeterminal 12 of the battery pack 10. The ES terminal 204 is connected tothe ES terminal 14 of the battery pack 10. The Rx terminal 205 isconnected to the Tx terminal 15 of the battery pack 10. The TS terminal206 is connected to the BD/TS terminal 16 of the battery pack 10. The Txterminal 207 is connected to the Rx terminal 17 of the battery pack 10.The TFB terminal 208 is connected to the Vcc/TFB terminal 18 of thebattery pack 10. The TD terminal 209 is connected to the TD terminal 19of the battery pack 10.

The working machine body 200 includes no counterpart terminal to thecenter terminal 13 of the battery pack 10. Thus, in response toattachment of the battery pack 10 to the working machine body 200, thecenter terminal 13 of the battery pack 10 is not electrically connectedto the working machine body 200 and is electrically open.

The working machine body 200 includes a motor drive circuit 211, a motor212, a drive mechanism 213, an output tool 214, a drive switch 215, aswitch drive circuit 216, the manipulator 217, a manipulation detectioncircuit 218, a drive control circuit 220, an ES input circuit 224, an Rxcircuit 225, a TS input circuit 226, a Tx circuit 227, a TFB outputcircuit 228, a TD output circuit 229, and a power-supply circuit 230.

The battery power is input to the motor drive circuit 211 from thepositive terminal 201 and the negative terminal 202. The motor drivecircuit 211 supplies electric power to the motor 212 based on a drivecommand input from the drive control circuit 220. The motor 212 isrotated with the electric power supplied from the drive control circuit220. The drive mechanism 213 transmits the rotation of the motor 212 tothe output tool 214. The output tool 214 is driven with a rotationalforce of the motor 212 via the drive mechanism 213. The output tool 214is configured to achieve a function of the electric working machine byacting on an object outside the working machine body 200. The outputtool 214 may be, for example, a rotary blade for cutting grass,small-diameter trees, and so on. Alternatively, the output tool 214 maybe, for example, a drill bit for making a hole in a workpiece. Stillalternatively, the output tool 214 may be, for example, a blade forblowing or sucking air.

Provided on a current path between the positive terminal 201 and themotor drive circuit 211 is the drive switch 215 to establish orinterrupt this current path. The drive switch 215 is controlled by thedrive control circuit 220 via the switch drive circuit 216.

The manipulator 217 is manipulated by the user of the electric workingmachine. The manipulation detection circuit 218 detects manipulation ofthe manipulator 217 by the user. In response to detection of themanipulation by the user, the manipulation detection circuit 218 outputsa manipulation detection signal to the drive control circuit 220 and tothe TD output circuit 229. In response to input of the manipulationdetection signal to the drive control circuit 220, the drive controlcircuit 220 turns on the drive switch 215 and drives the motor drivecircuit 211, to thereby rotate the motor 212.

A battery voltage Vp is input to the TS input circuit 226 from thepositive terminal 201. The TS input circuit 226 outputs a batteryvoltage Vb depending on the impedance of the BD/TS terminal 16 of thebattery pack 10. Specifically, if the input impedance of the BD/TSterminal 16 of the battery pack 10 is the above-described firstimpedance, the TS input circuit 226 outputs the input battery voltage Vpas the battery voltage Vb via a not-shown switching element. If theinput impedance of BD terminal 16 of the battery pack 10 is theabove-described second impedance, the TS input circuit 226 stops outputof the battery voltage Vb. The battery voltage Vb is input to thepower-supply circuit 230 and to the TFB output circuit 228.

The battery voltage Vb output from the TS input circuit 226 is input tothe TFB output circuit 228. The TFB output circuit 228 steps down theinput battery voltage Vb, and outputs the stepped-down battery voltageVb from the TFB terminal 208 as the above-described body detectionvoltage.

The power-supply circuit 230 converts the battery voltage Vb into acontrol power-supply voltage Vdm in a DC voltage. The controlpower-supply voltage Vdm has a voltage value lower than the voltagevalue of the battery voltage Vb. Relevant portions within the workingmachine body 200, including the drive control circuit 220, are operatedwith the control power-supply voltage Vdm.

The ES input circuit 224 is connected to the ES terminal 204. The Rxcircuit 225 is connected to the Rx terminal 205. The TS input circuit226 is connected to the TS terminal 206. The Tx circuit 227 is connectedto the Tx terminal 207. The TFB output circuit 228 is connected to theTFB terminal 208. The TD output circuit 229 is connected to the TDterminal 209.

In the present embodiment, the ES input circuit 224 has the sameconfiguration as the ES input circuit 74 in the charger 40.Specifically, the ES input circuit 224 outputs the ES permission signalor the ES prohibition signal described above. The ES prohibition signalis input to the drive control circuit 220 and to the switch drivecircuit 216.

If the ES permission signal is input to the drive control circuit 220,the drive control circuit 220 drives the motor 212 in accordance withmanipulation of the manipulator 217. If the ES prohibition signal isinput to the drive control circuit 220, the drive control circuit 220stops operation of the motor drive circuit 211 and turns off the driveswitch 215 even if the manipulator 217 is manipulated. If the ESpermission signal is input to the switch drive circuit 216, the switchdrive circuit 216 enables control of the drive switch 215 by the drivecontrol circuit 220. However, if the ES prohibition signal is input tothe switch drive circuit 216, the switch drive circuit 216 disables thecontrol of the drive switch 215 by the drive control circuit 220, andforcibly turns off the drive switch 215.

The Rx circuit 225 receives the transmission data transmitted from thebattery pack 10 via the Rx terminal 205, and relays the received data tothe drive control circuit 220. The Rx circuit 225 may be configured, forexample, similarly to the Rx circuit 75 in the charger 40.

The Tx circuit 227 relays, to the battery pack 10, the transmission dataoutput from the drive control circuit 220. The Tx circuit 227 may beconfigured, for example, similarly to the Tx circuit 77 in the charger40.

The TD output circuit 229 outputs the above-described manipulationsignal indicating whether the manipulator 217 is manipulated, based onwhether the manipulation detection signal is input from the manipulationdetection circuit 218. This manipulation signal is output to the batterypack 10 via the TD terminal 209.

(5) Terminals Arrangement in Battery Pack and Charger

In the battery pack 10, the positive terminal 11, the negative terminal12, the center terminal 13, the ES terminal 14, the Tx terminal 15, theBD/TS terminal 16, the Rx terminal 17, the Vcc/TFB terminal 18, and theTD terminal 19 are arranged as shown in FIG. 7. The center terminal 13actually includes two divided terminals 13 a and 13 b as shown in FIG.7. The divided terminals 13 a and 13 b are electrically connected toeach other and have the same potential. FIG. 7 shows a state in which anarrangement surface on which these terminals are arranged is viewed in adirection orthogonal to the arrangement surface.

In the charger 40, the positive terminal 41, the negative terminal 42,the center terminal 43, the ES terminal 44, the Rx terminal 45, the BDterminal 46, the Tx terminal 47, and the Vcc terminal 48 are arranged asshown in FIG. 7. FIG. 7 shows a state in which an arrangement surface onwhich these terminals are arranged is viewed in a direction orthogonalto the arrangement surface.

The battery pack 10 is attached to the charger 40 by being moved withrespect to the charger 40 in an attachment direction. The attachmentdirection corresponds to a leftward direction in FIG. 7. The batterypack 10 attached to the charger 40 is removed from the charger 40 bybeing moved with respect to the charger 40 in a removal directionopposite the attachment direction. The removal direction corresponds toa rightward direction in FIG. 7. A direction orthogonal to theattachment direction and the removal direction is hereinafter referredto as an orthogonal direction.

As shown in FIG. 7, in the present embodiment, the ES terminal 14, theTx terminal 15, the BD/TS terminal 16, the Rx terminal 17, the Vcc/TFBterminal 18, and the TD terminal 19 of the battery pack 10 are arrangedin two rows in the removal direction and arranged in three rows in theorthogonal direction.

Specifically, the ES terminal 14, the BD/TS terminal 16, and the Vcc/TFBterminal 18 are aligned at specified intervals in the orthogonaldirection. That is, the positions of these three terminals in theremoval direction coincide with one another.

The Rx terminal 17 is aligned with the ES terminal 14 in the removaldirection (with a specified distance away from the ES terminal 14 in theremoval direction). That is, the position of the ES terminal 14 in theorthogonal direction coincides with the position of the Rx terminal 17in the orthogonal direction.

The Tx terminal 15 is aligned with the BD/TS terminal 16 in the removaldirection (with a specified distance away from the BD/TS terminal 16 inthe removal direction). That is, the position of the BD/TS terminal 16in the orthogonal direction coincides with the position of the Txterminal 15 in the orthogonal direction.

The TD terminal 19 is aligned with the Vcc/TFB terminal 18 in theremoval direction (with a specified distance away from the Vcc/TFBterminal 18 in the removal direction). That is, the position of theVcc/TFB terminal 18 in the orthogonal direction coincides with theposition of the TD terminal 19 in the orthogonal direction.

If the battery pack 10 is completely removed from the charger 40, asshown in FIG. 7, the respective terminals of the battery pack 10 are notconnected to their counterpart terminals in the charger 40.

In response to start of attachment of the battery pack 10 to the charger40 by moving the battery pack 10 with respect to the charger 40 in theattachment direction, a positional relationship between the battery pack10 and the charger 40 is changed as shown in FIG. 8, for example.Specifically, the positive terminal 11 of the battery pack 10 contactsthe positive terminal 41 of the charger 40. The negative terminal 12 ofthe battery pack 10 contacts the negative terminal 42 of the charger 40.The center terminal 13 (specifically, the divided terminal 13 b) of thebattery pack 10 contacts the center terminal 43 of the charger 40. TheES terminal 14 of the battery pack 10 contacts the Tx terminal 47 of thecharger 40. The BD/TS terminal 16 of the battery pack 10 contacts the Rxterminal 45 of the charger 40.

That is, the Rx terminal 45 and the Tx terminal 47 of the charger 40temporarily contacts their non-counterpart terminals in the process ofattaching the battery pack 10 to the charger 40. The non-counterpartterminals refer to terminals different from the terminals in the batterypack 10 counterpart to the Rx terminal 45 and the Tx terminal 47 (i.e.,terminals different from the respective terminals to be connected to theRx terminal 45 and the Tx terminal 47 in response to complete attachmentof the battery pack 10).

Further movement of the battery pack 10 with respect to the charger 40in the attachment direction from the position of the battery pack 10shown in FIG. 8 changes the positional relationship between the batterypack 10 and the charger 40 as shown in FIG. 9, for example. In thepositional relationship shown in FIG. 9, the terminals of the batterypack 10 are connected to their counterpart terminals in the charger 40.Thus, in the positional relationship shown in FIG. 9, the battery pack10 is not completely attached to the charger 40, but the battery pack 10is electrically connected to the charger 40 completely.

Further movement of the battery pack 10 with respect to the charger 40in the attachment direction from the position of the battery pack 10shown in FIG. 9 allows the battery pack 10 to be completely attached tothe charger 40 as shown in FIG. 10.

In order to remove the battery pack 10 attached to the charger 40 asshown in FIG. 10 from the charger 40, the battery pack 10 is moved withrespect to the charger 40 in the removal direction. Movement of thebattery pack 10 in the removal direction changes the positionalrelationship between the battery pack 10 and the charger 40 in a mannerreverse to attachment of the battery pack 10 to the charger 40. Thus,for example, the Tx terminal 47 of the charger 40 is removed from thecounterpart Rx terminal 17 of the battery pack 10, and then, temporarilycontacts the non-counterpart ES terminal 14, in the process of removingthe battery pack 10 from the charger 40.

(6) Positions where ES Terminals are Arranged

In the present embodiment, the ES terminal 14 of the battery pack 10 andthe ES terminal 44 of the charger 40 are arranged such that anon-counterpart terminal in the battery pack 10 does not contact the ESterminal 44 of the charger 40 in the process of removing the batterypack 10 from the charger 40. More specifically, in the presentembodiment, each of the ES terminals 14 and 44 is arranged in thecorresponding most upstream area in the removal direction. Thus, the ESterminal 44 does not contact the other terminals of the battery pack 10following removal from the ES terminal 14.

The main reason why the ES terminal 44 is configured not to contact anon-counterpart terminal in the battery pack 10 in the removal processas described above is to inhibit a malfunction of the ES input circuit74 in the charger 40. The malfunction of the ES input circuit 74 asmentioned here includes unintended output of the ES permission signalfrom the ES input circuit 74.

Here, a hypothetical situation will now be discussed in which, forexample, the positional relationship between the ES terminal 44 and theTx terminal 47 in the charger 40, and the positional relationshipbetween the ES terminal 14 and the Rx terminal 17 in the battery pack 10are opposite to those shown in FIG. 7. Specifically, in such asituation, the ES terminal 14 is arranged downstream of the Rx terminal17 in the removal direction, and the ES terminal 44 is arrangeddownstream of the Tx terminal 47 in the removal direction. In thissituation, the battery pack 10 is attached to the charger 40, and thebattery 20 is charged by the charger 40. That is, in this situation, theline switch circuit 58 is turned on, and the charging current from themain converter 54 to the battery pack 10 flows through the positiveelectrode line 55. Further, in this situation, the battery pack 10 isremoved from the charger 40 while the battery 20 is being charged.

In such a situation, in response to removal of the ES terminal 44 of thecharger 40 from the ES terminal 14 of the battery pack 10 in the removalprocess, a signal output from the ES input circuit 74 in the charger 40is changed from the ES permission signal to the ES prohibition signal.This causes a forcible turning-off of the line switch circuit 58.However, in immediate response to the forcible turning-off of the lineswitch circuit 58, the charging control circuit 60 outputs the PWMsignal due to the influence of the above-described time lag and so on.Thus, the main converter 54 operates as normal despite the turning-offof the line switch circuit 58. As a result, a voltage value V1 (see FIG.2) between the line switch circuit 58 and the main converter 54 on thepositive electrode line 55 increases, and thus, difference between thevoltage value V1 and a voltage value V2 (see FIG. 2) between the lineswitch circuit 58 and the cell group switching circuit 57 increases.

In response to further progress of removal of the battery pack 10, theES terminal 44 contacts the non-counterpart Rx terminal 17. As describedwith reference to FIG. 6, the input impedance of the Rx terminal 17 is alow impedance. Thus, the state in which the ES terminal 44 is in contactwith the Rx terminal 17 is electrically equivalent to the state in whichthe ES terminal 44 is in contact with the ES terminal 14 of the batterypack 10 during input of the permission command to the ES output circuit24 in the battery pack 10. As a result, in the charger 40, the ESpermission signal is output from the ES input circuit 74 to turn on theline switch circuit 58.

In response to turning-on of the line switch circuit 58 in the statewhere the voltage value V1 is higher than the voltage value V2, thedifference between the voltage value V1 and the voltage value V2 maycause excessive current to flow through the line switch circuit 58, thusdamaging the line switch circuit 58.

The malfunction of the ES input circuit 74 may be caused not only by thecontact of the ES terminal 44 with the Rx terminal 17 but also bycontact with any other terminals (e.g., the Tx terminal 15) in thebattery pack 10 having a low input impedance (corresponding to theabove-described low impedance).

To cope with this, the battery pack 10 and the charger 40 of the presentembodiment are configured such that, in the removal process, the ESterminal 44 does not contact any terminals in the battery pack 10following removal of the ES terminal 44 from the ES terminal 14.

The ES terminal 14 corresponds to one example of the third battery packterminal of the present disclosure, the Rx terminal 17 corresponds toone example of the second battery pack terminal of the presentdisclosure, and the Vcc/TFB terminal 18 corresponds to one example ofthe first battery pack terminal of the present disclosure. The ESterminal 44 corresponds to one example of the third charger terminal ofthe present disclosure, the Tx terminal 47 corresponds to one example ofthe second charger terminal of the present disclosure, and the Vccterminal 48 corresponds to one example of the first charger terminal ofthe present disclosure. The battery control circuit 23 and the ES outputcircuit 24 correspond to one example of the state setting circuit of thepresent disclosure. The ES input circuit 74 corresponds to one exampleof the functional circuit of the present disclosure, and the mainconverter 54 corresponds to one example of the charging circuit of thepresent disclosure. The positive electrode line 55 corresponds to oneexample of the electric power path of the present disclosure, and theline switch circuit 58 corresponds to one example of the switch circuitof the present disclosure. The charging control circuit 60 correspondsto one example of the switch control circuit of the present disclosure,and the switch drive circuit 59 corresponds to one example of theenabling circuit and the forcible interruption circuit of the presentdisclosure. The range lower than or equal to the first thresholdcorresponds to one example of the specified range of the presentdisclosure.

The embodiment of the present disclosure has been described so far;however, the present disclosure is not limited to the above-describedembodiment and can be practiced in variously modified forms.

Other Example Embodiments

(1) The ES terminals 14 and 44 may be arranged such that, in the processof removing the battery pack 10, the ES terminal 44 contacts anon-counterpart terminal in the battery pack 10 having a high inputimpedance (corresponding to the above-described high impedance)following removal of the ES terminal 44 from the ES terminal 14.

FIG. 11 shows a specific example of such arrangement. In FIG. 11, the ESterminal 44 is arranged in a downstream area in the removal direction.Arranged in an upstream area in the removal direction is the Vccterminal 48. Thus, in the process of removing the battery pack 10, theES terminal 44 contacts the Vcc/TFB terminal 18 of the battery pack 10following removal from the ES terminal 14.

As described with reference to FIG. 5, the Vcc/TFB terminal 18 of thebattery pack 10 has a high input impedance. Thus, even in the case wherethe ES terminal 44 contacts the Vcc/TFB terminal 18, a malfunction ofthe ES input circuit 74 in the charger 40 is not caused.

The non-counterpart terminal (specifically in the present embodiment,the terminal having a high input impedance) configured not to cause amalfunction of the ES input circuit 74 even in contact with the ESterminal 44 as described above may be arranged so as to contact the ESterminal 44 in the process of removing the battery pack 10.

(2) The terminals of the battery pack 10 and the charger 40 may bearranged in a different manner from that shown in FIGS. 7 and 11. Forexample, the non-counterpart terminal in the battery pack 10 having alow input impedance (i.e., the non-counterpart terminal that may cause amalfunction of the ES input circuit 74 in response to contact with theES terminal 44) may be arranged so as to pass through an area notincluding the ES terminal 44 of the charger 40 in the process ofremoving the battery pack 10.

In other words, the ES terminal 44 may be arranged so as not to contactthe non-counterpart terminal in the battery pack 10 having a low inputimpedance in the process of removing the battery pack 10.

For example, in FIG. 7, the Vcc/TFB terminal 18 may switch positionswith the Tx terminal 15 (or with the BD/TS terminal 16 or the TDterminal 19). For example, in FIG. 7, the Rx terminal 17 may switchpositions with the Tx terminal 15. For example, in FIG. 11, instead ofthe Vcc/TFB terminal 18, another terminal (e.g., the BD/TS terminal 16)having a high input impedance may be arranged in the position where theVcc/TFB terminal 18 is arranged. For example, in FIG. 7, the ES terminal14, the BD/TS terminal 16, and the Vcc/TFB terminal 18 do notnecessarily have to be arranged in a line in the orthogonal direction.The same applies to the positional relationship of the Rx terminal 17,the Tx terminal 15, and the TD terminal 19.

Further, the total number of the terminals of the battery pack 10 andthe charger 40 is not limited to that in the above-described embodiment,and the battery pack 10 and the charger 40 may include any number ofterminals.

(3) The ES input circuit 74 of the charger 40 and the ES output circuit24 of the battery pack 10 may be configured in any manner. In theabove-described embodiment, the ES input circuit 74 is provided with thePNP-type bipolar transistor (the switching element T42) in its inputstage. In another example embodiment, the ES input circuit 74 may beprovided with, for example, a PNP-type bipolar transistor in its inputstage, and may be configured to output the ES permission signal or theES prohibition signal by turning-on or turning-off of this transistor.

The ES output circuit 24 may be configured to, for example, turn on theabove-described transistor by outputting a HIGH-level signal to a baseof the above-described transistor via the ES terminal 14 in response toinput of the permission command from the battery control circuit 23. TheES output circuit 24 may be configured to, for example, turn off theabove-described transistor by outputting a LOW-level signal to the baseof the above-described transistor via the ES terminal 14 in response toinput of the prohibition command from the battery control circuit 23.

Even in the case where the ES output circuit 24 is configured as above,the ES terminal 44 of the charger 40 may be arranged so as not tocontact the non-counterpart terminal in the battery pack 10 that causesa malfunction of the ES input circuit 74 by contact with the ES terminal44 (i.e., that turns on the above-described transistor) in the processof removing the battery pack 10.

(4) Two or more functions of a single element in the above-describedembodiments may be achieved by two or more elements, and a singlefunction of a single element may be achieved by two or more elements.Two or more functions of two or more elements may be achieved by asingle element, and a single function achieved by two or more elementsmay be achieved by a single element. Part of the configuration of theabove-described embodiments may be omitted. At least part of theconfiguration of the above-described embodiments may be added to orreplaced by the configuration of the above-described other embodiments.

What is claimed is:
 1. A charging system comprising: a battery packconfigured to be removably attached to an electric working machine; anda charger configured such that the battery pack is removably attachedthereto, the battery pack including: a battery configured to be chargedwith charging power supplied from the charger; a first battery packterminal having a high input impedance; a second battery pack terminalhaving a low input impedance or being configured to have the low inputimpedance in response to the battery pack being in a normal state, thesecond battery pack terminal being spaced apart from the first batterypack terminal in an intersecting direction, the intersecting directionintersecting a removal direction of the battery pack from the charger; athird battery pack terminal aligned with the first battery pack terminalor with the second battery pack terminal in the removal direction; and afirst circuit configured to set the third battery pack terminal suchthat the third battery pack terminal has the low input impedance, inresponse to the battery pack being in the normal state, the low inputimpedance being lower than or equal to a first threshold, the high inputimpedance being higher than a second threshold, and the second thresholdbeing higher than or equal to the first threshold, the chargerincluding: a first charger terminal configured to be connected to thefirst battery pack terminal in response to attachment of the batterypack to the charger; a second charger terminal configured to beconnected to the second battery pack terminal in response to attachmentof the battery pack to the charger; a third charger terminal configuredto be connected to the third battery pack terminal in response toattachment of the battery pack to the charger; and a second circuitconfigured to output a first signal in response to connection of thethird charger terminal to the third battery pack terminal having the lowinput impedance, the second battery pack terminal being arranged so asto pass through an area spaced apart from the third charger terminal ina process of removing the battery pack from the charger.
 2. A chargingsystem comprising: a battery pack configured to be removably attached toan electric working machine; and a charger configured such that thebattery pack is removably attached thereto, the battery pack including:a battery configured to be charged with charging power supplied from thecharger; a first battery pack terminal having a first electricalcharacteristic; a second battery pack terminal having a secondelectrical characteristic or being configured to have the secondelectrical characteristic depending on an operating state of the batterypack, the second battery pack terminal being spaced apart from the firstbattery pack terminal in an intersecting direction, the intersectingdirection intersecting a removal direction of the battery pack from thecharger; a third battery pack terminal aligned with the first batterypack terminal or with the second battery pack terminal in the removaldirection; and a state setting circuit configured to set, in response tothe battery pack being in a presupposed operating state, an electricalcharacteristic of the third battery pack terminal such that the thirdbattery pack terminal has the second electrical characteristic, thecharger including: a first charger terminal configured to be connectedto the first battery pack terminal in response to attachment of thebattery pack to the charger; a second charger terminal configured to beconnected to the second battery pack terminal in response to attachmentof the battery pack to the charger; a third charger terminal configuredto be connected to the third battery pack terminal in response toattachment of the battery pack to the charger; and a functional circuitconfigured to perform a first function in response to connection of thethird battery pack terminal having the second electrical characteristicto the third charger terminal, the second battery pack terminal beingarranged so as to pass through an area spaced apart from the thirdcharger terminal in a process of removing the battery pack from thecharger.
 3. The charging system according to claim 2, wherein the statesetting circuit is configured to determine whether a malfunction ispresent, the malfunction corresponding to an event in which charging ofthe battery has to be stopped in the battery pack, and the presupposedoperating state corresponds to a state in which the malfunction is notpresent.
 4. The charging system according to claim 2, wherein the firstfunction includes output of an operation permission signal, and whereinthe charger further includes: a charging circuit configured to generatethe charging power; an electric power path configured to supply thecharging power to the battery pack; a switch circuit configured toestablish or interrupt the electric power path; a switch control circuitconfigured to control the switch circuit; an enabling circuit configuredto enable control of the switch circuit by the switch control circuit inresponse to output of the operation permission signal; and a forcibleinterruption circuit configured to disable the control of the switchcircuit by the switch control circuit to thereby cause the switchcircuit to interrupt the electric power path, in response to no outputof the operation permission signal.
 5. The charging system according toclaim 2, wherein the state setting circuit is configured to set thethird battery pack terminal such that the third battery pack terminalhas, as the second electrical characteristic, a first input impedancewithin a specified range, wherein the first battery pack terminal has,as the first electrical characteristic, a second input impedance out ofthe specified range, and wherein the second battery pack terminal has athird input impedance within the specified range.
 6. The charging systemaccording to claim 2, wherein the state setting circuit is configured toset the third battery pack terminal such that the third battery packterminal has, as the second electrical characteristic, a first inputimpedance within a specified range, wherein the first battery packterminal has, as the first electrical characteristic, a second inputimpedance out of the specified range, and wherein the second batterypack terminal is configured to have a third input impedance within thespecified range depending on the operating state of the battery pack. 7.The charging system according to claim 2, wherein the third battery packterminal is aligned with the first battery pack terminal in the removaldirection.
 8. The charging system according to claim 2, wherein thethird battery pack terminal is aligned with the second battery packterminal in the removal direction, and wherein the third battery packterminal is arranged on an opposite side of the removal direction withrespect to the second battery pack terminal.
 9. A battery packconfigured to be removably attached to an electric working machine andto a charger, the charger including a first charger terminal, a secondcharger terminal, and a third charger terminal, the battery packcomprising: a battery configured to be charged with charging powersupplied from the charger; a first battery pack terminal configured tobe connected to the first charger terminal in response to attachment ofthe battery pack to the charger, the first battery pack terminal havinga first electrical characteristic; a second battery pack terminalconfigured to be connected to the second charger terminal in response toattachment of the battery pack to the charger, the second battery packterminal having a second electrical characteristic or being configuredto have the second electrical characteristic depending on an operatingstate of the battery pack, the second battery pack terminal being spacedapart from the first battery pack terminal in an intersecting direction,the intersecting direction intersecting a removal direction of thebattery pack from the charger; a third battery pack terminal configuredto be connected to the third charger terminal in response to attachmentof the battery pack to the charger, the third battery pack terminalbeing aligned with the first battery pack terminal or with the secondbattery pack terminal in the removal direction; and a state settingcircuit configured to set, in response to the battery pack being in apresupposed operating state, an electrical characteristic of the thirdbattery pack terminal such that the third battery pack terminal has thesecond electrical characteristic, the charger being configured toperform a first function in response to connection of the third batterypack terminal having the second electrical characteristic to the thirdcharger terminal, the second battery pack terminal being arranged so asto pass through an area spaced apart from the third charger terminal ina process of removing the battery pack from the charger.
 10. A chargerconfigured such that a battery pack is removably attached thereto, thebattery pack including a first battery pack terminal, a second batterypack terminal, and a third battery pack terminal, the charger beingconfigured to supply charging power to the battery pack, the chargercomprising: a first charger terminal configured to be connected to thefirst battery pack terminal in response to attachment of the batterypack to the charger, the first battery pack terminal having a firstelectrical characteristic; a second charger terminal configured to beconnected to the second battery pack terminal in response to attachmentof the battery pack to the charger, the second battery pack terminalhaving a second electrical characteristic or being configured to havethe second electrical characteristic depending on an operating state ofthe battery pack, the second charger terminal being spaced apart fromthe first charger terminal in an intersecting direction, theintersecting direction intersecting a removal direction of the batterypack from the charger; a third charger terminal configured to beconnected to the third battery pack terminal in response to attachmentof the battery pack to the charger, the third charger terminal beingaligned with the first charger terminal or with the second chargerterminal in the removal direction, the third battery pack terminalhaving the second electrical characteristic in response to the batterypack being in a presupposed operating state; and a functional circuitconfigured to perform a first function in response to connection of thethird battery pack terminal having the second electrical characteristicto the third charger terminal, the third charger terminal being arrangedso as to pass through an area spaced apart from the second battery packterminal in a process of removing the battery pack from the charger.